Preparation and lectin binding specificity of polystyrene particles grafted with glycopolymers bearing S-linked carbohydrates

Polystyrene particles bearing ATRP initiating groups, obtained by emulsifier-free emulsion polymerization of styrene (St) and 2-chloropropyloxyethyl methacrylate (CPEM), were subjected to surface-initiated activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP) using glycomonomers, i.e., 4-vinylbenzenesulfonamidoethyl 1-thio-β-d-glucopyranoside (1) and 4-vinylbenzenesulfonamidoethyl 1-thio-β-d-lactoside (2). The glycopolymer-grafted polystyrene particles obtained Gp1 and Gp2 were shown to have hydrated graft layers of 15–65 nm in thickness on the cores of 370 nm in diameter. Gp1 and Gp2 coagulated in the presence of concanavalin A (Con A) and that of peanut agglutinin (PNA), respectively, showing highly specific response toward lectins.     

B1-to-B2 structural transitions in rock salt intergrowth structures

The rock salt (B1) structure of binary oxides or chalcogenides transforms to the CsCl (B2) structure under high pressure, with critical pressures P(s) depending on the cation to anion size ratio (R(c)/R(a)). We investigated structural changes of A(2)MO(3) (A = Sr, Ca; M = Cu, Pd) comprising alternate 7-fold B1 AO blocks and corner-shared MO(2) square-planar chains under pressure. All of the examined compounds exhibit a structural transition at P(s) = 29-41 GPa involving a change in the A-site geometry to an 8-fold B2 coordination. This observation demonstrates, together with the high pressure study on the structurally related Sr(3)Fe(2)O(5), that the B1-to-B2 transition generally occurs in these intergrowth structures. An empirical relation of P(s) and the R(c)/R(a) ratio for the binary system holds well for the intergrowth structure also, which means that P(s) is predominantly determined by the rock salt blocks. However, a large deviation from the relation is found in LaSrNiO(3.4), where oxygen atoms partially occupy the apical site of the MO(4) square plane. We predict furthermore the occurrence of the same structural transition for Ruddlesden-Popper-type layered perovskite oxides (AO)(AMO(3))(n), under higher pressures. For investigating the effect on the physical properties, an electrical resistivity of Sr(2)CuO(3) is studied.     

Total syntheses of (+)-spiculoic acid A and (+)-zyggomphic acid, new marine natural products of polyketide origin

The total syntheses of both natural (+)-spiculoic acid A and (+)-zyggomphic acid, new cytotoxic marine natural products of polyketide origin, have been accomplished for the first time. These syntheses were achieved by the highly stereoselective and high-yielding intramolecular Diels-Alder reaction of a functionalized (E,E,E)-2,7,9-dodecanal derivative to construct the core tetrahydroindan-2-one skeleton. A stereocongener of (+)-spiculoic acid A, i.e., the (2R,5S,6R)-isomer, was also synthesized. The details of these total syntheses are described.     

Biomimetic engineering of modular bispecific antibodies for biomolecule immobilization

Modular bispecific antibodies (BsAb's) that interact directly with a gold surface were engineered for immobilization on biosensing devices. The BsAb's consist of the variable fragments of antigold and antilysozyme antibodies connected via one of three linkers derived from naturally occurring proteins. The BsAb's were bound tightly to both the gold surface and to lysozyme, thus functioning as interface molecules between lysozyme and the gold surface without a substantial loss of antigen-binding activity. The antigen-binding capacity (the ratio of the amount of immobilized lysozyme to the amount of immobilized BsAb) on the gold surface reached 82%. An analysis of the correlation between binding capacity and linker characteristics indicated that the presence of a long, rigid linker sequence derived from a cellulase resulted in a higher antigen-binding capacity than did the presence of a long but relatively flexible glycine-rich linker. This result suggests a strategy for designing linkers suitable for BsAb-based biomolecular immobilization.     

Photocontrol of cell adhesion on amino-bearing surfaces by reversible conjugation of poly(ethylene glycol) via a photocleavable linker

Dynamic control of cell adhesion on substrates is a useful technology in tissue engineering and basic biology. This paper describes a method for the control of cell adhesion on amino-bearing surfaces by reversible conjugation of an anti-fouling polymer, poly(ethylene glycol) (PEG), via a newly developed photocleavable linker, 1-(5-methoxy-2-nitro-4-prop-2-ynyloxyphenyl)ethyl N-succinimidyl carbonate (1). This molecule has alkyne and succinimidyl carbonate at each end, which are connected by photocleavable 2-nitrobenzyl ester. Under this molecular design, the molecule crosslinked azides and amines, whose linkage cleaved upon application of near-UV light. By using aminosilanised glass and silicon as model substrates, we studied their reversible surface modification with PEG-azide (M(w) = 5000) based on contact angle measurements, ellipsometry, and AFM morphological observations. Protein adsorption and cell adhesion dramatically changed by PEGylation and the following irradiation, which can be used for cellular patterning. Also, the capability of the substrate to change cell adhesiveness by photoirradiation during cell cultivation was demonstrated by inducing cell migration. We believe this method will be useful for dynamic patterning of cells on protein-based scaffolds.     

Rational creation of chiral multinuclear and metallosupramolecular compounds from thiol-containing amino acids

Developments in the rational creation of chiral multinuclear and metallosupramolecular compounds based on linear-type metal complexes with penicillaminate (pen), as well as their functionality as a multidentate chiral metalloligand, is the main subject of this paper. The reactions of a mononuclear Au(I) complex, [Au(d-pen)(2)](3-), in which two d-pen ligands bind to an Au(I) center through thiolato S atoms, with transition metal ions afford a variety of S-bridged heterobimetallic multinuclear complexes, the structures and properties of which are highly dependent on the nature of reacting metal ions. The created multinuclear complexes still act as a metalloligand when they possess free amine and/or carboxylate groups, leading to the formation of heterotrimetallic supramolecular structures by reacting with third metal ions. While the Au-S bonds in [Au(d-pen)(2)](3-) are generally retained in the course of the reactions with metal ions, this is not the case for the Hg-S bonds in the corresponding Hg(II) complex, [Hg(d-pen)(2)](2-). A remarkable chiral behavior of multinuclear complexes composed of [Au(l-cys)(2)](3-) (cys = cysteinate), which is opposite to that composed of [Au(l-pen)(2)](3-), is also presented.     

Peripherally cyclometalated iridium complexes of dipyridylporphyrin

Two types of novel iridium pincer complexes bearing a porphyrin backbone were synthesized and characterized from dipyridylporphyrin. One of the complexes has a Lewis acidic site on the iridium center in the mer-coordination mode. The other complex takes the fac-coordination, which is rarely observed in benzene-based pincer complexes.     

Stereocontrolled synthesis of (+)-methoxyphenylkainic acid and (+)-phenylkainic acid

The efficient total syntheses of (+)-methoxyphenylkainic acid (3) and (+)-phenylkainic acid (4) were achieved using a rhodium carbenoid-mediated intermolecular C-H insertion reaction. Complete stereoselective construction of the kainoid skeleton was accomplished by utilizing the stereochemistry at the C-4 position as a pivotal stereogenic center.